well keep in mind that his bike was set up for him (or her), if your friend is taller than you then yeah, you'll be stretched out. i actually found that i like riding a bike that's sized 2-3 cm smaller than what's recommended for someone my size. i rode a 56 cm for a while and when i got a new bike this past weekend decided to test ride some 53/54 cm frames and i ended up going with a 54. the top tube is a bit shorter, as is the seat tube, but when the shop fitted me everything came out feeling just perfect with a slightly longer stem, which they swapped out for free from their parts bin.

just test ride various sizes and see what feels best, and PLEASE don't let them adjust your reach to the handlebars with a saddle fore/aft adjustment. the shop where i got fitted on my first bike did this, and being the ignorant newb i was, didn't realize it compromised my leg positioning and i've been battling a case of patellar tendonitis ever since. adjust the seat height and fore/aft to get the proper fit for your lower body, and then a new stem (if necessary) for your upper body. you can pick up decent stems for $20-$30.