It was 2001/2002 when I met him, twice, but Sid (Alexander Siddig -- everyone calls him Sid, which is his real first name after all) was quite pleasant and friendly. Nothing over the top, nothing to disappoint. Very middle of the road. He falls into the big group most of them do, of nice and cordial. This was a decade ago now, though. I've heard he's grown a bit weary of the Star Trek connection since then. He's spoken on record that it's been a damper for getting other parts, but he does not go into the "I regret doing Trek" area. He just is honest that it can be a blessing and a curse.
He has some great stories. I can't do them justice, but I'll try so that, if you ever meet him, you could ask him to tell them himself...
Story of him and Colm Meaney getting together for a drink in a pub in Ireland. Sid goes to get the drinks, and the barkeep looks him up and down and says, "We don't server your kind here," which shocks Sid. He goes back to the table and reports this to Colm, suggesting he get the drinks, as he thinks the barkeep is upset with his Arab heritage. Colm starts laughing his ass off though, and finally says, "It's not that! It's cause you're
british!"
He also told a rather... questionable story? Also deals with the issue of race, but, it could be seen as insensitive to some. It's not meant as such. But anyway, looking like he does, he obviously gets looks when he's on a plane, especially in first class. Doesn't matter how he sounds, or that he's an actor. After 911, people see a middle-eastern-looking fellow on a plane, instinct is instinct, right? Well I don't know if he *did* this or just *thought* about doing this, but the action in question was to pretend to be sleeping as the plane landed, only to 'wake up' startled and disappointed and remark to the fact they'd landed as if he'd had other intentions.

I imagine that anecdote might ruffle a feather or two, but it's just a venting joke from the point of someone whose judged based solely on appearances sometime. Everyone laughed when he told it, lol.
Andy Robinson is a gem, IME. He loves Garak, and it's great if you can see him and Sid together. He's warm and friendly. Doesn't come off as a potential assassin like Garak at all, lol.
Addressing the Robert Beltran topic briefly...
Beltran is a dick. That's just who he is. He's been acting like a pompous dick since before Voyager ended, and he's kept right on doing so for a decade now. He won't go bending your ear with complaints unless you really engage him, but if you do, expect to get his honest disgruntled opinions on Voyager and Chakotay. He just wasn't left with a good taste in his mouth from it. Simple as that. The rest of the Voyager cast know this, even joke about how "grumpy" he is. *Shrug* What are you gonna do? It's his opinion, his experiences.
Marina Sirtis, she is fun, but her sense of humor can be a little snarky. It can strike you as bitchy unless you realize, it's just her individuality asserting. She loves Trek and her fans.
Tim Russ, I love. He does (or did, back then 10 years ago) this Star Trek spoof skit. I'm not a stage person, but I volunteered and was picked, went up on stage with him and a few other fans. Did my lines, had fun. Did a decent job, too, surprisingly, lol. As far as I know, I'm the only fan who ever got to keep their script of his skit. I learned this later from his sister, Angela, who I talked with on e-mail. I'm sworn to keep it secret, even though there is likely video of the skit being performed out on YouTube, lol. He also did me a favor, which I'm quite grateful for. He recognized me in the autograph line for being in the skit, repeated his thanks, and signed an extra item for me -- a second Voyager cast photo. He then smacked Garrett Wang on the shoulder and had him sign it for me, too, without me even needing to ask.

Which is why I have a season 3 cast photo with Kes signed by the whole cast save Kes, and a season 6 with Seven signed complete.
Denise Crosby is very loving of her fans. She flirted with me once. Hehe. I was 16 at the time, but I'm really tall, so I easily passed for 18! I was surprised at how attractive she was (decade ago) seeing as that she was easily twice my age and such, lol. She really likes when fans do something a little different. I had an 8x10 of her and Data printed up and signed, and she was enthusiastic about that. I'm also well known in my circle of friends for coming up with GREAT inscription quotes, and for her, I took her final line from TNG: "No Good-byes, just good memories" and she really loved signing that, that I'd thought of such.
I really want to meet Nana Visitor again. My health won't really let me, though. I've done this epic photoshop manipulation of her as Captain Kira and had it printed into an 8x10 and want to have it signed, and give her a double I made just for her. She *LOVED* wearing the SF Uniform in the end of DS9, about cried when they took it back from her. She talks about Kira as if she's a real person that exists somewhere, which I love. Oh, and she's got the baseball! Hehe. Sisko's baseball.
http://browse.deviantart.com/?qh=§ion=&q=Captain+Kira+Nerys#/d128cjh << Captain Kira.