I wouldn't recommend buying a computer *before* an introductory tech course - what you (should) learn in that course is the information that will enable you to make a choice, between a computer and/or a bottom timer.
For an introductory course, a "recreational" computer in gauge mode is perfect. What you are really doing in the course is demonstrating that you have the skills to do a moderate amount of deco - the dives you do after the course should be fairly conservative and "routine", so a bottom timer and tables really should suffice.
Computers are a tool, and like all tools need to be "fit for purpose" and also "properly used" in order to do the job they are intended to do. Sure, you can work wood with a flathead screwdriver - but you'll get a much better result if you use a chisel.
There are two issues to consider. First of which is whether the computer is barrier to learning principles. Jumping in and following a computer is easy - when it works, but if you learn the computer rather than the principles of decompression, then (a) you are probably limiting your diving and (b) what do you do when something goes wrong.
Personally, I have major issues with the use of any computer that doesn't let you plan your dive in it's entirety. Yes, you can cut some tables using Vplanner then do the dive using a Suunto - but the Suunto won't give you the same profile as Vplanner. So if Vplanner says to stop at 21m, but the Suunto is saying 9m.... what do you do?
No offence intended to those people who use Ratio Deco 100% of the time - but I think that you've forgotten what it's like to start using RD. I think for RD to "make sense" and to make reasonable decisions about your profile then you need some form of baseline. For experienced divers that baseline can be the 100s of dives you have done using RD - but for newer divers, that baseline is probably some custom tables cut from desktop planning software. As a relative newbie to using RD, I still start with Decoplanner and compare what RD gives me for my plan and contingencies with profiles generated using VPM and Buhlmann and create some pragmatic profiles that suit my dive.
At present, I use a number of computers and/or RD - depending on the dive. I've used Suunto Vytec, VR3, Shearwater Pursuit and an OSTC mkII. I am using my OSTC almost exclusively now on both recreational and technical dives. On some dives, I still use my Vytec in gauge mode as the primary took and run the OSTC next to it "for information". This is because (a) I am geeking out, and (b) it's an experimental computer and I am wanting to see what it does under certain dive profiles.
The nice thing with the OSTC (which applies to the Shearwater as well) is that it can be set up to essentially mirror a RD profile. For OC diving, the OSTC is probably better featured and better value than the current Shearwaters - but the OSTC is to all intents and purposes entirely experimental, so it is not for everyone.