Website said to have stood up to rush to buy 500,000 remaining tickets for Games, but some would-be customers dissatisfied.

London 2012 organisers said their ticketing system stood up to a huge influx of potential buyers as remaining Olympic tickets went on sale on Wednesday morning, although some customers complained of long waits and an unwieldy booking system.

Previous sales rounds were blighted by criticism over the way tickets were allocated and technical difficulties, but organisers said the Ticketmaster website had withstood an initial rush that ticketing experts expected to match the hunt for Take That tickets when the group re-formed.

About 500,000 tickets were made available on Wednesday to allcomers on a first come, first served basis. The most recent sales phase was restricted to those who had failed to secure a ticket in earlier rounds.

While those who had succeeded in purchasing tickets took to Twitter and other social networking sites to say they were happy with the system, others complained about the erratic countdown clock that was supposed to tell them how long to wait and the frustration of a system that took up to half an hour to check whether particular tickets were still available.

The London Olympic organising committee, Locog, which has come under fire for its ticketing policy in the face of huge demand for the 6.6m tickets available to the general public, said that as Wednesday's sale began there were still £20 tickets remaining for the boxing, fencing, football, table tennis, taekwondo, volleyball, weightlifting and, with limited availability, judo and wrestling.

There was "good availability", but at higher price points from £45 to £450, for archery, badminton, basketball, beach volleyball, canoe sprint, diving, handball, hockey.

There was limited availability and only at higher prices for the race walk, mountain biking, artistic gymnastics, rowing, sailing and water polo.

General entry tickets for the Olympic park, put on sale at £10 towards the end of the last sales phase, were also available alongside 1.4m remaining football tickets. The majority of park tickets, of which there are 70,000 on sale so far, are for the first week of the Games when it will be less busy because the athletics has yet to start.

A further 150,000-200,000 tickets are to be released back on to the market, including some for previously sold-out sessions, as seating configurations are finalised, and will be added to the system as they become available.

Locog will also put tickets for the main climb in the cycling road race and the cycling time trial at Hampton Court on sale next week at £15. The move has proved controversial, with cycling fans used to watching the action from the side of the road for nothing.

On the same day, 29 May, general access tickets to the tennis tournament at Wimbledon – allowing access to Henman Hill and the outside courts but not the show courts – will also be made available.

London 2012 organisers – who had warned that users would face waits of half an hour on the site at peak times – this week defended their record on ticketing, insisting that they had managed to balance fairness with revenue raising.

"Do I think we have delivered the fairest possible system? I absolutely do," said the Locog deputy chairman, Sir Keith Mills. "We got it about as right as we could. We wanted to hit our revenue targets, we wanted full stadiums and we wanted to treat everyone as equally as we could."

-Owen Wilson