So I'm considering getting my first 1911, what I really want is an original World War 2 era 1911A1, but since I can't afford that I'm looking at clones, right now I have found a Tisas, I have never heard of them until last night, how do they compare?  By that I mean other than maker (and presumably cast parts) what specifically are the difference between a Tisas 1911A1 clone, and an original 1911A1?

Finish?
Grips?
Parts?
Machining of the frame, or slide?
Sights?
Materials?
Anything?

Further what about the model it'self?  Is it a good company?  Is it reliable?  Is it accurate?  How is the customer service?  Is there a warranty, and if so does it transfer to the new owner, or does it apply to the first buyer only?  Is this equal to, worse, or better than a Rock Island?

Also I'm considering trading an XD45 for one (both used) is that a decently good deal, or would I be screwing myself?

Tisas 1911s are made in Turkey and they have cast frames and mostly cast parts, just like RIA.

They are also sold by Umarex and Interstate, both series 70 and 80 (without and with the firing pin block, respectively ) have been imported.
Machining looks to be the typical good quality that Turkish guns seem to be showing these days.
IMHO, they are a cut above RIA in the machining dept.

But, on the flip side, the Tisas guns are still too new and few to have proven themselves to be made with the QC and tolerances right consistently, like RIA does these days.
You are buying a newcomer's gun, with the risk and lower price point that implies.

Tisas 1911s sell for $350-$399 new street price, so I'd want the 1911 and cash for an XD45.

I have owned a GI style Tisas 1911 for about nine months and have fired a little over 500 rds through it. So far, it has been 100% reliable with no malfunctions. It has fed ball ammo as well as Federal HST, Hydra Shok and Winchester RA45T with no failures. I have found it to be more accurate than I had expected it to be for a sub-$500 1911. I have had good luck using Wilson 47D, CMI Hybrid 8 rd and the MecGar 8 rd mags. I am not sure how compatible it will be with aftermarket parts as I have only replaced the recoil spring with a Wilson 18 lb and the included firing pin spring. Overall, I am quite happy with the pistol and you can see several reviews on Buds Guns website.

In addition, I purchased one of the Tisas 1911A2 ehnhanced pistols last week and hope to get it to our local range this coming weekend. One thing I have noticed so far is that on this model the slide will not lock back when using any of the four MecGar mags I have, but does lock back with the Wilson 47D and CMI mags. The single initial complaint I have with the A2 model is that the beavertail safety is loose and sloppy. Not sure why they could not have done a better job of fitting the grip safety since the rest of the pistol is rather tight fitting. These are not high end or high dollar 1911 pistols, but if the A2 performs as well as the GI model has, I will be quite happy with both of these 1911 models for what they are (entry level 1911's).