I carry a sub XD9 daily. I went with 9mm due to getting my (at the time) gf a pistol that was chambered in 9mm and didn't want to stock too many calibers. Now I've got so much around that it doesn't make sense to change.
Its a nice size (like the Mill Pro and mini-Glocks) for daily carry while still chambering a service caliber. I've ran +P loads without any issues. It can (like many other down-sized service pistols) use its larger brothers magazines. It doesn't have a manual safety that you can forget to dis-engage when drawing for real but does have a grip safety to help cover your butt.
If you like 1911's but want something lighter, smaller and probably cheaper to carry, an XD is it.
Size wise it is a little larger than a mini-glock or KT P11. You may not be able to get your pinkie on the grip, I had to add a Pearce Plus Zero grip adapter to mine.
My dad's got an XD .45 Tactical, and it's a very nice piece. I'm not really a fan of striker-fired pistols as a rule (other than my PT145), but shooting the XD is a pleasure. I can't comment too much on reliability since all I've fired through it has been either WWB or Remington UMC JHPs, though it didn't have any kind of problems with those two rounds. The accuracy is great, too; I'm just an average shot, but I can easily get all 13 rounds touching at moderate distances with it.
I have 2 XD's (a sub .40 and a .45 4-inch compact).
They are about as reliable as a semi-auto can be IMO. Many people like them for various reasons not limited to 1. grip safety 2. a little heftier than a baby Glock but still concealable 3. ambi mag release 4. priced around $40 less than Glock 5. You get the XD gear package with them.
I own a Tactical model in .45 ACP and can't praise this gun enough. I like the ergos, the sights are easily acquired, it's sturdy, reliable, accurate and have had zero issues of any type with it. NYPD said all the rest.
There is one con I forgot to mention there are a lot of dicks on there website (xdtalk.com). You can get good info from the site but is not near as friendly as this site. So get the gun but come back here to talk and show pics.
I've had my XD for 4 years give or take. I don't even remember what all I've fed that thing. I had a bobble with Blazer Aluminum but it doesn't care about Wolf (powder coat) so who cares. I know that I've shot American Eagle, WWB, Blazer Brass, Fiochi and Magtech (I think).
Mine's consumed quantities of Corbon 115gr JHP's and WWB 115gr JHP's with any issues. I haven't tried enough of anything else yet to be 100% sure but I will be testing 124gr +P Gold Dots. I tried a small sample (20rds) and it was fine but I want to run another 50+ before I'm totally confident.