As the majority of my work is education and public sector based, we started getting invitations to tender at various times when the team first started out. It's only now that I've the confidence, time, contacts and tools to really get stuck into these and I'm glad I've finally submitted a hefty quote for a college I have on my accounts. Some tenders are pretty awful to wade through though, and perhaps some of the more competitive suppliers just don't have the time to inspect a mammoth document and fullfill every whim or desire on it.
The one big advantage a buyer has with this is that I can submit the specs out the parts to all the major brands and get them to bid it down. We also encourage the buyer to take the time to get someone to show you a product if you're rolling out on a big scale. There's nothing worse than tendering for something only to change your mind halfway through and have to start again. Worse still, you can take delivery and find it's just not what you wanted. Ask them for evaluations, demos, most suppliers should be happy to let either show off their products or arrange an evaluation, especially if it's a cutting edge solution they're wanting to show off. Wherever possible, most specifications can be met but don't be suprised if you're asked why because some weird and wonderful specifications turn up in quotes and it just completely baffles account managers who just don't know or understand why you'd need some things.
Possible disadvantages are that due to having to price a quote up for maybe a month or two in advance, you might find yourself paying more due to how volatile pricing can be, especially if the product suddenly drops in price or a competitor brand decides to go head to head with a similar product you've asked to have quotes on.