Something about his size is off. Height. Width. Something. Most folks I talk to over on the collecting sites think Hasbro screwed up in some manner or another with the new Artoo's scale compared to the humanoid characters. I suppose it's a matter of opinion and debate, but as fantastic as this R2-D2 looks and with all the great accessories and tools he comes with there's just something awry and off about his size and he doesn't look quite right next to the X-Wing Luke.
He should be a little taller or a little wider/fatter. Maybe a bit of both. I dunno, if I and OdoWan
and others are wrong then fine, but it seems to be a strong and dominant opinion with collectors at the moment.