Still worth the purchase?

I would say refresh your Surface RT. I too thought the 8.1 upgrade impacted performance noticeably.

The first thing I did was clear up space on the eMMC as I noticed before if it dropped below 4 GB free space, it slowed down.

The next thing I did was refresh the system. It was amazing how much faster the system was clean. Still not a speed demon but definitely usable.

But if you can swing for a Surface 2, that machine is much faster.
 
I got a Asus t100 last year and last I got a surface rt (swapped my old ps3 for it ��) I always wanted a RT but I wanted full windows for uni but wow the surface is amazing 8.1 is buttery smooth I find it one of the best devices I've ever used the build quality is top notch even the camera is decent with the RT being on par with an IPad while the pro is more of a laptop it is far and wide the best netbook style tablet I've ever used yes I'm sure the 2 is better but the next generation is always better lol