Our group has a decent array of experience in this area, although I wish that weren't the case.
For the brief period of time we played 2e, there were only four members of or group including the DM. To avoid a small party or having the DM control several NPCs, we decided to have each player create and control 2 characters. Overall, I'd say it worked fairly well, but it certainly isn't optimal. There were more than a few occasions where a player clearly acted in the best interest of one PC over the other, or simply forgot the full range of capabilities each character provided.
More recently, our group has expanded to seven people which is great. The problem now, of course, is coordinating a mutually acceptable gaming time for everyone. Generally, five or six of us are able to attend, and we play the PCs of those who are absent. During those sessions, the absent player's character is used primarily in support by employing their most basic function throughout the session: fighting; healing; spellcasting; scouting.