You should be aware of the many reports that the disc has and so, purchasing the digital format is the best way to go for it.
Episode 1 & 2 = Free
Episode 3 & 4 = 200 MSP (£2.00)
Episode 5 = 400 MSP (£3.50)
Sure as shit I wouldn't buy the retail disc version for this price if it was available here, maybe it'd cost £20 to £25. BUT
if it comes out on disc for Xbox 360 / PS3 I'll consider for £20-£25!
Edit: TellTale would have to make sure to fix all bugs that the disc edition has, though.