Since that disastrous case, then Chief Justice Arthur Chaskalson chose not to appoint an acting judge to the Constitutional Court as he was entitled to by section 175 of the Constitution. Now new Chief Justice Pius Langa has decided to appoint acting judges again and I am not sure this is a good thing.
In a closely contested case, an acting judge appointed by the Chief justice in consultation with the Minister of Justice, may hold the deciding vote. In the Chaskalson era those judges almost always voted with the Chief Justice. This means that the Chief Justice can temporarily "pack" the Court with his/her appointees and can help to secure a majority in cases where the permanent judges might normally have a majority.
Because South Africa's Constitutional Court is not particularly divided on ideological grounds this has not yet been an issue but in years to come it may become decisive. In future, some judges may even decline to take sabbatical in fear of "ceding" his or her vote to the "opposition", which would be rather unfortunate.
At the same time acting judges do get a chance to take part in deliberations of the Constitutional Court and can thus be "groomed" for a post on the highest court. Still, not an ideal situation.