Of course the drawbacks of using SLI/Crossfire include:
- Double power usage
- Double Heat
- Double Noise
- A lot less space for expansion cards (especially for double slots GPUs)
- Doesn't always perform as well as a single card for the combined price (or less), although this depends on many factors, such as the types of cards and game etc.
- Different games take more or less advantage of an SLI setup, some even suffer from a Dual GPU setup.
But SLI does certainly help run games at above 1920 where all but the chunkiest GPUs struggle with newer games.
Anyhow my 2c.