I've had a play with a Surface RT and really liked it. Personally I'd take the Surface Pro over an iPad, as it feels like you can be more productive with the Surface. Fewer silly, unnecessary apps to get distracted by, Microsoft Office is there, and the touch cover is really nice to type on.
If you're wanting something primarily for fun, then the iPad is probably a better choice. Personally though, I think for working, the Surface Pro would make more sense.
Well my main issue is that I have a bunch of paid apps on the iPad. Which if I got a new one i would transfer over. I think the main issue i have with the Surface is the OS space is not seperate from the total space, the 128gb you only get approx 84 free GB (according to reviews I saw), and 64gb you get about 30gb which basically sucks. The nice part tho is you can add more with a microSD. I do like that it is a 'full' OS and can do almost anything a desktop can do, but at the same time then why would I not just get an ultrabook for a few more $$.
I won't touch anything Apple with a 10m pole on principle. Typically not a fan of tablets/etc (they're just not efficient for real work).. but awhile back I picked up an ASUS TF300T with the keyboard dock. Very solid tablet, and even despite Android it makes a pretty decent netbook.
I do a lot of work from my iPad. The limitations of any device are based on the hardware and/or user. The question is which do you think is going to please you more. Maybe write down 10 things that matter and then organize by how much they matter. Figure out which one is going to annoy you the least. Principle irrelevant, it's not a marriage, just a device
If it's just a tablet you're after then get the Surface RT. It's cheaper and will get you a longer battery life.
I was looking at buying a laptop/tablet hybrid these past few months and I've definitely considered the Surface Pro. At the end of the day I didn't find a bit over 4 hours of powered-on time to be completely satisfying, despite it's other attractive features. Personally I'm looking forward to the Haswell devices which are not far-off - you'd probably do best by waiting a bit as well. You might not want to wait all that long because it's your birthday, but you should at least consider an alternative gift or a coupon at your favourite electronics retailer.
I'd say go for a Nexus 7/10 or similar high quality Android device. I played around with a Surface in the store before I bought my Nexus and wasn't impressed. If you need full fledged Windows on the go, there might as well buy a netbook/ultra portable as it will cost you even less than Surface Pro but likely have better features/battery life and a real keyboard to type with.
I'm extremely happy with my Nexus, it's a quality piece of hardware and I have no trouble getting 8 hours + battery life with fairly heavy usage. It's still a mobile and it shows but almost anything you can think of has an App, except for an NX client apparently!.
TLR, the Surface RT seems crappy and the Pro version is so expensive that it doesn't pay to get one unless you're really a Microsoft fanboy. They make similar keyboard/covers for most tablets.
I bought the Surface RT at launch last year; at the time I already had a iPad1, iPad2, the Asus Transformer and a Windows traditional tablet. When I need a tablet, I still usually use the iPad2. I am used to the entertainement and audio/video apps and I find the general experience good enough. The Safari web browser is not the greatest thing on this tablet; I tap to the Chrome app when needed.
The Asus Transformer (Android) has better browser and better IT-related apps; I use it for Wi-Fi and network scanners, terminal emulators etc. I usually leave it at the office.
The surface RT strongly reminds me of the old-style Windows tablets. The hardware build is top-quality, even better than Apple (magsafe power supply, integral metal stand etc). But the app selection is lacking. Best free apps are the preloaded office 2013 home and student suite and the Internet Explorer 10 browser. I use it rarely, often as traditional portable, hooked up to keyboard, mouse, and sometimes external full-hd monitor. It also has a very good remote resktop client. Surface Pro should be the same, without the no-legacy-windows-app limitation but with the added weight and limited battery time of a traditional notebook. It could be a good choice if you need a new laptop with touch features.