The Beck spyder is an interesting proposition... Very attractive, classic lines, insane power to weight ratio, and all of the handling prowess of a nearly 60 year old design... ;-)
I remember a review from years ago (I don't even remember which magazine) in which they tested a "standard" Beck Spyder against one with a CB special motor. The standard one was fast, and the articulate response from the driver of the hot one was something like - "Scary as hell, man!" (whimpering)
Where a prime advantage of the Elise is raw handling capability, the 550 Spyder does not really share that advantage, and while the Beck Spyder has been slightly improved (including more modern tire design, etc.) it's a real stretch to compare it to an Elise! Talk to anyone who has driven a 550 fast in the twisties, and they'll tell you some hair raising stories of how the car (mis)behaves at the limit. Great eye candy, classic ride, but not really a driver's car! We have been very spoiled by the steady progress of modern automotive technology...
Still, if somebody gave me a Beck Spyder for my birthday, I'd probably keep it!
Of course, if an Elise is a stretch financially for people, a lot of the above cars are out of reach too. To add to the out of reach list, the other car I drool about (also British...interesting theme we've got going) is the Noble M12 GTO which is now available in the US at http://www.1gracing.com/ . The website doesn't have prices listed, but I have read somewhere you can fit it out for about $70K.