Here's the deal in short
If you get Lightroom 3 then upgrade to Lightroom 4 the controls will be different so if you have no experience of either you will have to learn new stuff when you are only just onto the learning curve
But buying 3 then upgrading to 4 might be cheaper than than buying 4 outright when it released ... It might not, but lr3 can be had quite cheap now and upgrades are usually aprox £100
Lightroom 3 is cheaper now as when 4 is released there will be no updates ... No updates means any new cameras won't be recognised by 3 after 4 is released
Lightroom 4 when released will be full price ie c.£250
Lightroom 4 will be better
Any photos processes in LR3 will be recognised by 4 with the option to update the edit to 4 but updating will change the effect on the photo
Using a beta always has its risks but is free until 4 is officially released, at which point you will have to buy it
I haven't tried 4 as I have decided for the sake of workflow it is best to leave it until the final version is out ... This decision is based on haveing clients relying on getting photos to the on time ... This might not always be possible with a beta ...
Although the beta doesn't replace the previous version I don't have the time to play with 4 beta really ...
I will upgrade to 4 the day it is released (as I have done with 2 from 1 and 3 from 2)
So... My advice, to an ameture just starting out with this sort of softwarw, without commitments to clients looking to go down the very sencible road of Lightroom is to get 4 beta now as it will give you a chance to get use to the new fetures ... It might cost a little more in the long run, but not much!
