Define "good"? Putting the workflow issues aside and only looking at the
image quality when scanning medium format, it goes roughly like this, in the ascending order:
- Dirt cheap camera-based setup with an extension tube
- Epson V600
- Epson V700/750/850
- Plustek 120 Pro
- Mid-priced camera-based setup with a macro lens
- Coolscan 8000/9000
- Flextight 949/X5
- High-end camera-based setup
- Creo
- Drum
The definition of cheap/mid-priced/high-end camera setups deserves a thread of its own. Mainly this is about megapixel count, lens quality, availability of pixel-shifting and stability of the platform.
Also, there's the law of diminishing returns. Starting from the middle of this list each subsequent upgrade costs progressively more money while offering smaller marginal improvement than a previous upgrade.