Has anyone upgraded to Stage 1 using the BSR portable programmer like the one ElkParts has up for sale for £558? Had any problems?

Just had a quote from my local Dealer for the Hirsch Stage 1 remap for £995 fitted (ouch).

I realize the BSR one will void the warranty but hey ho, if they do the same job then my wallet will dictate future choices

Also just been fitted for a new anorak.