I'd say go 48/16 myself; the bike looks nice, which is one of the main reasons I won't buy one myself (in the process of buying my first fixed gear as well).

I am going with a Rob Roy and coughing up the extra on a flip flop. I personally like the color of the Roy better, IRO is a name that I've come to think of as synonymous with track bikes and has a reputation. Add in that Tony is a regular poster here and its a shoe in that I'm giving him my business. Raleigh has a solid background, but appears to have become yet another large scale, mass production pit that I'd prefer not hand my money to.

Sadly, budget does affect how we do things, but think like this:

For $599+shipping I can get a better grade bike (better quality frame, min.) and all I have to do is buy the flip flop hub and switch it over (okay, i have to buy a lockring too, but let's not get pickie). For $100 more I upgrade the headset and I'm in a good position.

But I digress, the issue I have with most of the bottom grade fixed gear bikes is this, your not paying for a lot of extra, expensive dura ace components (or whatever your prefered manufacture is) and therefore you can save a lot already, cutting corners on a fixed gear is like buying a custom IF frame or a Dean and throwing on Sora components and WTB tires on Alex 2000 rims.

If your going to go, put quality above all; Your paying for a frame, bb, one brake and a wheelset (give or take) I say cough up the funds to make it worth your while and last, not be something you regret having to dump funds in later to upgrade/upkeep and have a ride.

/shrug, my 2cents, which aren't worth much. YMMV.